As others have said - build your own. It's honestly not as hard as it looks, just treat it as one giant jigsaw puzzle.
Ok, I'm from the UK here, so please bare with me regarding pricing differences :)When building a PC for about £350 (roughly the equivalent), I would allocate £50 to the motherboard, £50 to the power supply, £20 for the case, £60 for the graphics card, £60 for the processor, £15 for a disk drive, £35 for the RAM, £60 for the hard drive (or reuse the existing one, and format it). Plus you need to factor in an operating system, keyboard, mouse, monitor, printer, and speakers/headphones should you be replacing any of them.
Something like:
MotherboardRAMHope this points you in the right direction :) Good luck!